They voted for him, yet a growing number of American liberals are angry over President Barack Obama’s reliance on the use of drones and his support for the National Defense Authorization Act. They argue that the president’s embrace of these policies is even more extreme and conservative than that pursued by his predecessor, George W. Bush.

“If Bush had done the same things as Obama, then more people would have been upset about it,” Daniel Ellsberg observed. “He is a Democrat, though, and to an extent can get away with it.”

Ellsberg, who is famous (or notorious, depending on one’s political preferences) for having leaked the Pentagon Papers in 1971, is among the plaintiffs in a court case challenging the NDAA. He and others have accused the Obama administration of using the law to grant itself unconstitutional new powers.

“In order to protect us from terrorism, the government is taking away our constitutional rights,” said Michael Moore, the controversial liberal filmmaker and activist who made the anti-Bush documentary “Fahrenheit 9/11.”

For its part, the government vigorously denies that the NDAA threatens ordinary citizens and it has appealed a judge’s ruling that the act is unconstitutional, arguing that the White House must have such powers if it is to successfully fight terrorism.

Critics insist the broad language used in the act to define what constitutes a terrorist or what actions amount to support for terrorist groups could unfairly impede journalists, activists and academics. The case, now on appeal in New York, could reach the Supreme Court.

Liberals are also greatly concerned about the Obama administration’s expansion of the use of unmanned drones to attack suspected militants, and the president’s nomination of John Brennan to head the Central Intelligence Agency has only heightened the criticism. Brennan, one of Obama’s most trusted advisers, has been a major proponent of the use of drones.

Many Americans, in and out of government, see significant advantages to the deployment of drones, mostly because they do not put any pilots at risk. However, they have created deep resentments in Afghanistan, Pakistan, Somalia and Yemen where drone attacks have killed innocent civilians as well as suspected jihadists (including at least one American citizen, Anwar al-Awlaki, who was identified as a major figure in the planning of attacks on the country of his birth, and, significantly, his teenage son).

And some critics ask that if the United States believes it is legally justified in using drones as military weapons overseas, what’s to stop America’s enemies from embracing the same logic and sending their drones to attack this country?

Obama also faces pressure to make public secret documents that lay out his administration’s legal rationale for killing suspected terrorists (including American citizens such as al-Awlaki). Some are comparing Obama’s national security policy to that of the Bush administration’s reliance on secret legal memos to justify torture techniques such as waterboarding.

“The parallels to the Bush administration torture memos are chilling,” Vincent Warren, executive director for the Center for Constitutional Rights, observed. “Those were unchecked legal justifications drawn up to justify torture; these are unchecked justifications drawn up to justify extrajudicial killing.”

The president is not without support. His 2008 election opponent, Sen. John McCain of Arizona, and two other Republican senators filed a court brief in defense of the NDAA, arguing that the policy is necessary on national security grounds.

Which side is right? As long as terrorism remains a genuine threat to America’s security, the debate will rage. And, in a way, that’s a triumph for the terrorists.